
\section{Introduction}
\label{sec:intro}
\begin{figure}
  % Requires \usepackage{graphicx}
  \includegraphics[width=3.3 in ]{Figures/mobile.eps}\\
  \caption{An example of the mobile community.}\label{figure:mobile}
\end{figure}


%mobile 's significance and popularity of mobile search and application(some survey and examples)

Mobile communication is a fast growing industry and mobile is an
ubiquitous platform for relationship-building, learning,
entertainment, commerce, and social networking. With the huge amount
of mobile users worldwide and latest technology for easy wireless
access to the internet, mobile becomes another significant device
besides desktop for data access. Mobile search plays a major role in
meeting the growing users' demand for information from anywhere and
anytime. Also, the past few years saw an increasing usage of popular
internet applications on mobile devices, including email, maps and
instant messaging. Consequently, there is enormous market
opportunity on mobiles, in particular, for advertising and
recommendation system. Many recent research projects,[][][],are
using the rich mobile data for interesting applications and mining.



%hetergenous data, relationship between each other, hard to manage

A new generation of mobile phones, smartphones have been brought to
the market in the last few years. For example, Nokia N900 released
recently. The availability of those GPS-enabled smartphones with
sensors can help us collect valuable data, such as location, speed,
outside temperature, orientation, etc. These data, as well as
message, emails, user's profile, calender and event compose a rich
data source for the business purposes mentioned above. Furthermore,
all these information have internal relationship with each other to
large extents. For example, Peter had an event "graduation ceremony"
on July 5th in his calender on his mobile, he also took the photos
of him wearing a baccalaureate gown with his friends on that day.
Moreover, from his messages with his friends, we can easily find
their interest on that ceremony. The mobile can also record the
temperature everyday in July. Figure \ref{figure:mobile} describes
the example. \(Another example is needed here.\)

In order to manage the various heterogenous data collected from the
mobile, we need a kind of representation structure which is simple
but expressive enough for utilization by as many types of
applications as possible. Ontology is used to define basic terms and
relations comprising a vocabulary, as well as rules for combining
the terms and relations. Given the graph structure of ontology, we
can link different types of information using friendship, ownership,
and co-occurrence of time and location. For example, in figure 2,
the circle nodes represent different users while the triangle nodes
represent different photos taken by these users. And the edge in red
means the friendship while the edge in green means the ownership.

%mobile query is a simple and necessary task of all the application
%different applications are independent and we need a unified toolkit
Quite a few related studies have been conducted to develop various
novel applications on mobile devices. For example, MobileMiner
\cite{ wang:mobileminer} is a real world data mining tool in mobile
communities. Several researchers have done some research about
spatial mining given the the pervasiveness of GPS-enabled device.
For instance, in \cite{ zheng:learning}\cite{ zheng:location}, the
authors make use of the raw data collected from the GPS devices, and
mine some valuable and interesting information like the
transportation mode and classical travel sequences in a region. Of
all these applications, mobile querying is a basic and necessary
task. Also, fast and efficient mobile query is important for both
users and business purposes.
\begin{itemize}
  \item {\em For users.} Mobile users want to access and manipulate
  information and services specific to certain situation. A mobile
  query system can help users reflect on their past events and
  deeply understand their life patterns as well.
  \item {\em For Business purposes.} There are tremendous market opportunities
  on mobile applications, especially for advertising business.
  Mobile  query plays a significant role in facilitating and
  manipulating the mobile context through the device.
\end{itemize}
However, the query process in different applications on mobiles are
independent and a unified toolkit for mobile query is needed to
facilitate and improve the performance of all the applications and
services on the mobiles. For the best of our knowledge, there is no
unified toolkit for mobile query released online and this is our
focus in this work.

Traditional keyword-based query can return all the objects
containing the keyword. However, it has several disadvantages for a
keyword-based query on mobile: 1)Since there are many different
types of data on mobile, sometimes we need to differentiate them,
for example, for a query "sports meeting", we want to get all the
SMSs talking about the sports meeting rather than some photos taken
that day. 2)The heterogenous data on mobiles are interdependent and
have many inner relationships so that results only based on keyword
might ignore many implicit but valuable information based on the
structural relationships. For example, /(some examples are needed
here/).Consequently, in this work, we want to make use of both the
textual description of different objects, like the keyword-based
query goes, and the structural relationship between them, which can
be viewed as graph query.


%Client computing to solve some problems of server computing
Moreover, due to the following two reasons, when mobile data is used
for the purposes of immediate interaction, like the query in our
work, it is not feasible to continuously send high sampling rate
data to a distributed server over the air for analysis and then back
to the device for the results. 1) User might be unwilling to share
his/her private information to the server and to pay the
communication fee. 2)The information exchanged between server and
client will introduce burden of communication and be vulnerable to
data loss or delay. In this paper, we want to design and implement a
device-centric mobile query, which needs no or little support of the
remote server. For the best of our knowledge, few related work has
been done to device-centric mobile query.

The restriction of querying for mobile context includes the
following issues: less computing power, less memory capacity,
restricted network access capability, lower bandwidth, higher price
of data transfer, varying network transfer rates, varying
availability of network and limited battery capacity. As discussed
previously, in this work, we focus on the device-centric mobile
query toolkit, which can solve the problem related to the network
access capability, lack of infrastructure and possible delays in
network communication.


%our contribution: 1)client computing 2) keyword plus structural 3)Reduce cost of speed and memory4) a unified toolkit, applicability, nokia sharing system

In this paper, we try to make the following contributions:
\begin{itemize}
  \item  We present a device-centric client computing query system, which needs no external support of a remote server and is free from the communication delay or loss.
  \item  In terms of query, we use both the textual description and structural link information to get both the explicit and implicit results.
  \item  Due to the limitation of computation power and capacity of mobiles, we implement an efficient and fast query method with low cost of memory and time.
  \item  We develop a unified toolkit, Mquery, for further
  applications. And we will use it in NOKIA photo sharing system(more needs to be added here to show the high applicability of Mquery).
\end{itemize}


%the paper map
The rest of the paper is organized as follows: \secref{sec:problem}
defines the preliminary concepts and briefly formulates the problem
of graph query for mobile context; \secref{sec:approach} explains
the proposed approach. Our performance study is reported in
\secref{sec:exp}. Related work is discussed in \secref{sec:related}
 Finally,
\secref{sec:conclude} concludes our study.

%\secref{sec:exp}
%illustrates several applications of TAP on real datasets.
